agedhorse

Both this PLUS the dynamic (burst) power factor and voicing into the perception of loudness. There are switchmode power supplies that are far more stout than line frequency supplies, and have very high duty cycles as well. Like everything in life, there are good and bad examples of both line frequency and switchmode power supplies.

This is an important aspect of both perception and actual power. When a typical tube amp is driven hard by players looking for that kind of tone/texture, they are often driving the amp well beyond 10% THD which represents both an increase in power as well as an increase in volume due to the harmonics falling into a region where the ear is more sensitive. In fact, this is one reason for the popularity of some Darkglass models (using solid state power amps plus drive algorithms). The native voicing of an amp will also come into play, as well as the increase in average power (a form of compression) when these amps are driven hard. The same thing can be done (with varying degrees of success) with solid state power amps and suitable engineering, but it comes fairly naturally with many (not all) tube power amps.

Part of the reason for Randy's statement is because the burst power was significantly higher than the continuous power. The power supply is not typical, there is an awful lot of energy storage which holds the supply voltage higher than is typical. While it's a little harder on the tubes, the clean (or undistorted) dynamic power increase is few dB over the continuous power rating which, along with the voicing choices, contributes to a loud, dynamic sounding amp. While the continuous power is around 350-400 watts RMS, the dynamic (also called burst but rather than 20mSec, it's closer to 100mSec) power is closer to 600-800 watts RMS. This is on the 400+ with capable tubes.

Maximum output level depends on the capability of the output stage, it has to have enough voltage swing capability to reproduce whatever input level x gain requires for undistorted or unclipped output.

(Voltage) Gain is output level divided by input level. Maximum output level it the voltage that an output can deliver without clipping. You can have high gain but all it does is clip because there’s not enough output level to reproduce the unclipped signal, that’s the basis for distortion pedals. The two parameters are relatively unrelated, you can look this up on a good engineering website.

It's NOT gain that's the issue, it's the maximum output level which is an entirely different parameter.

Yes, as Paul said, this is one of the things that the direct output covers. While the owner's manual addresses interfacing with mixing consoles in detail, exactly the same applies to recording interfaces. Be sure you identify what signal level(s) your interface wants to see.

And this is WHY a full set of specs is so helpful. There are very few products in the bass/guitar world that provide this necessary information, which requires an unhealthy amount of guessing to arrive at a solution. Then again, it's also necessary to understand the specs.

Go watch Eurovision The Movie. It's silly, campy, in marginal taste, but funny and very well done.

It’s not gain or gain structure but limited maximum output level of many (not all) pedal preamps that’s responsible for not being able to drive a power amp to rated output. if a power amp has an input sensitivity of +4dBu (power amp sensitivity is measured with the input level control all the way up), the preamp must have a maximum output level capability of AT LEAST +4dBu (I recommend 6dB more if possible) in order to achieve rated power. The output impedance of the driving device (preamp) should be roughly 1/10th (or less) the value of the input impedance of the driven device (power amp). If not, there will be additional losses. In the case where the output impedance is 12k and the input impedance is 10k, there will be a ~6dB loss. Unfortunately, these specs are often omitted (or unknown/unmeasured) by manufacturers which makes matching a crapshoot. As an example of a pedal preamps that’s that can easily drive a power amp to rated output, the Genzler Magellan Pre-Di is one. It also includes all of the important, necessary specs to document the performance: Specifications DIMENSIONS: 6” (152mm) W x 4.3” (110mm ) D (w/ jacks) x 2.5” (63mm) H (w/ knobs and feet) WEIGHT: 1.1 lb (0.5kg) POWER SUPPLY: 9VDC-18VDC (low noise type), either polarity, 80mA POWER SUPPLY JACK: 2.1mm center pin with 5.5mm barrel (standard Boss pedal dimensions) INPUT IMPEDANCE: 1 Meg Ohm INPUT SENSITIVITY (nominal): -10dBu to -20dBu (instrument level) INPUT SENSITIVITY (maximum): >0dBu (9V supply), >+5dBu (12V supply), >+10dBu (18V supply) HIGH PASS Filter Range: 25Hz – 120hz, 18dB/oct variable EQ Filter Points: LOW: +/-15dB shelving below 75 Hz MID: +/-15dB peak-dip, between 150Hz – 2.8kHz HIGH: +/-15dB shelving above 6kHz PREAMP OUTPUT IMPEDANCE: 1k ohm (unbalanced), 2k ohm (balanced) PREAMP OUTPUT LEVEL (nominal): -10dBu to +4dBu (line level) PREAMP OUTPUT LEVEL (unbalanced maximum): +8dBu (9V supply) +12dBu (12V supply), +16dBu (18V supply) PREAMP OUTPUT LEVEL (balanced maximum): +14dBu (9V supply) +18dBu (12V supply), +22dBu (18V supply) DIRECT OUTPUT LEVEL (balanced nominal): -30dBu (mic level) DIRECT OUTPUT IMPEDANCE: 2k ohm (balanced) AUX INPUT IMPEDANCE: 10 K Ohm AUX INPUT LEVEL (nominal): -10dBu, stereo (sums to mono) AUX INPUT LEVEL (maximum): +10dBu, stereo (sums to mono) HEADPHONE OUTPUT: Drives headphones and IEM buds from 8 ohms -200 ohms, stereo output, mono signal path. (Higher impedance headphones, such as 600 ohms, will result in less output and headroom.)

That’s the reason for annealing and part of the reason for the dome shape (the other primary reason is to improve the HF radiation pattern). Work hardening and subsequent fatigue fracturing occurs when there is repeated flex in a material that is stiff in nature. As a practical example, JBL successfully perfected this process on their aluminum dust caps and high frequency diaphragms, they can last a lifetime if not abused.

My suggestion is to contact Surrey Amps, this is pro level service and Stan Lawrence is a highly qualified and experienced service engineer who is fully capable of taking care of Subway amps. I can support him at the factory level too. https://surreyamps.co.uk/contact-us

That's a cosmetic treatment, unrelated to the real thing except in looks. Proper aluminum dust caps are formed then annealed so that they resist cracking/fracture. This is no different than how (quality) high frequency diaphragms are manufactured.

It was around 2000-2001, the project was called "Indigo" (a dual concentric + sub music foreground/commercial audio product) and my job was to help them migrate the power amp from BASH technology (which went bankrupt) to ICEPower. This was long before Uli Behringer acquired them.

That's a short lived model that I never ran across. I didn't do anything with the studio side of the market, only the live/install side. It looks like yours is an aftermarket recone because that's not what the factory workmanship would be (based on my experience with the company). This looks to be a factory part:

I wonder if that was some kind of experimental application, doesn't look at all like a factory product. I did a fair amount of work for Tannoy many years ago, and at that time they were all about clean appearance and workmanship.

I can’t say that I have ever seen a Tannoy cone like that. Are you sure that’s a real Tannoy cone/product?

Things get super exciting when neutrons move...

The simplest and most well known example of off axis extension is the Duraluminum dust cap that attaches directly to the bobbin. It radiates the HF component of the signal like a 4” driver. The Duraluminum material is the same material that jBL developed for use in high frequency compression drivers. A wizzer cone is not a separate transducer, it’s just a specialized dust cap that attaches to the top lip of the bobbin just like the JBL aluminum dust cap. How well the HF energy coupled to the secondary radiation device determines in part the effectiveness. Decoupling the dust cap from the bobbin can be used to alter the response, as does the choice of materials.

There’s the basic premise of destructive interference due to the diameter of the driver versus the mid-high frequency wavelength, but this is modified by the size/shape of the dust cap and the geometry of the cone. With the right choices, the mid polar pattern can be altered more than an octave above what the basic predictions suggest. this can be taken to an even higher level by the use of a “wizzer cone” dust cap.

700 watts RMS is 1400 watts peak and 2800W peak-to-peak. You forgot the squared factor in the formula.

Yet there are several mechanisms that are used to improve off axis high frequency extension. This is why some 15” designs are better than others in this regard.

It could be any number of issues. If the OP is in the US then any QUALIFIED, Ampeg authorized service center should be capable of properly diagnosing the fault (the first step in any repair) and then repair the amp. If the OP is in the UK, Surrey Amps is qualified and capable of handling the diagnostics and repair.

As you have probably learned, a little reverb on bass goes a long way, and just a little too much can quickly become a bigger problem than what you are trying to solve.

Cooling an amp in a way that's effective, quiet AND reliable is a lot harder than it appears. The fans that are featured as "super quiet" usually do not have the airflow , especially under any static pressure losses that a cooling system presents. The D-800 has a fairly expensive ball bearing fan that's reasonably quiet (not as quiet as the sleeve version by a dB or two) but is very long life (about 50k hours compared with about 5-10k hours of a typical sleeve bearing fan). It also runs continuously at a slow speed because the resulting air flow allows multiple components to stabilize thermally together as a system. It's extremely unlikely to ever run any faster than the slowest speed, even at 2 ohms. Back about 15 years ago, when I was working at another company, I led a research project (with the cooperation and support of ICEPower R&D) that specifically addressed a whole slew of thermal and dynamics/duty cycle management design approaches, which resulted in a US Patent relating to this application. Some of what we learned, and how they relate to bass guitar ended up being incorporated into the newer ICEPower modules.